The Philippine government said Wednesday it would counter efforts by Beijing to formally assign Chinese names to undersea features in Benham Rise, a vast Pacific Ocean plateau east of the Philippines that Manila has declared as its territory.

The Philippine embassy in Beijing raised concerns with the Chinese government and was considering notifying international hydrographic and oceanographic agencies that deal with the mapping and naming of underwater features to complain about this, presidential spokesman Harry Roque said.

“We object and do not recognize the Chinese names given to some undersea features in the Philippine Rise,” Roque said in a statement, using another name for Benham Rise.

The United Nations has recognized Benham Rise as territory of the Philippines, which has been locked in a dispute with China and several Southeast Asian countries over the South China Sea off the west side of its archipelago.

Beijing apparently applied to the agencies last year to assign Chinese names to some features of Benham Rise. During international meetings held in Brazil in 2015 and 2017, China had proposed names for several of its undersea features, according to Roque.

The Philippine government last week declared a freeze on all foreign explorations in Benham Rise, after several nationalist groups had protested when a Chinese research vessel was granted access to the vast but largely unexplored sea region.

In 2012, the U.N. designated the rise as within the territorial jurisdiction of the Philippines, thus giving the country the sole right to exploit natural resources in the area. The 13-hectare region lies about 250 km (155.3 miles) east of the northern coast of Isabela province.

‘Passivity of the Duterte administration’

In 2017, Philippine President Rodrigo Duterte signed an order renaming the region the “Philippine Rise.” It is believed to be rich in mineral deposits and marine life, including tuna.

While China has not contested the area, applying to assign Chinese names to some Benham Rise features raised suspicions from nationalist groups and politicians in the Philippines.

On Wednesday, Sen. Paolo Benigno Aquino said Benham Rise was clearly a Philippine territory and China had no business there.

“It is imperative that we protect our territory from foreign interests,” he said.

Rep. Gary Alejano, an opposition lawmaker, called on President Duterte to be more “assertive and consistent in exercising the exclusive rights” of the country over others.

“The government must be resolute in asserting our rights and protecting our territory instead of downplaying threats of Chinese encroachment,” Alejano said. “The audacity of China, to the extent of naming features found within our very own territory is reinforced by the passivity of the Duterte administration.”

China’s move was meant to normalize its “aggressive and all too often unlawful maritime behavior,” he said, adding, “The adverse implications of which are the erosion and ultimately, the concession of the Philippines’ sovereign rights over the region.”

Last week, Duterte ordered the armed forces to escort any foreign ships that may stray into the area by accident out of the territory. This came after the government was put on the defensive when reports emerged that China had sent survey ships into the area.

The Philippines has insisted that foreign ships were allowed into the area, and that there had been as many as 30 foreign licenses granted to survey the area, including from the United States and China.

If China was allowed to rename some Benham Rise features this early, it likely would lay claim to the entire region, said former National Security Adviser Roilo Golez, who has remained active in intelligence circles.

“That is what I anticipate. This is a long-term objective for them, maybe 10 to 20 years,” Golez said, noting that was China’s effective strategy in the South China Sea.